Which GCC 10 default change causes link failures for tentative globals?
Background Local builds compiled with GCC 9 link successfully even when the same uninitialized global variable appears in multiple translation units. In production, after upgrading to GCC 10+, the same source fails with “multiple definition” errors. Root Cause GCC 10 changed the default handling of tentative definitions from -fcommon to -fno-common . The lin